1. Field of the Invention
The present invention relates to a liquid crystal display device and, more specifically, to a liquid crystal display device in which almost the entire display area is brought into a transparent state for a condition behind it to be clearly viewed, so that only a specific pattern isolated in the display area is displayed in a scattering state.
Further, the invention specifically relates to a liquid crystal display device which is installed in a finder optical system of a camera to be suitable for displaying a target pattern for autofocus in a finder visual field.
2. Description of the Related Art
A liquid crystal display device using a liquid crystal display panel (LCD) has an advantage of thin-profile, light weight and, additionally, an extremely low power consumption, and thus it has been used as displays of wide-ranging devices including various kinds of portable electronic devices such as electronic calculators, cellular phones, wristwatches, cameras, video cameras, notebook personal computers, and the like.
In the liquid crystal display panel, a pair of transparent substrates are coupled together with a fixed gap provided therebetween with a sealing part provided around a display area, and the gap is filled with a liquid crystal layer to constitute a liquid crystal cell. Then, voltage is partially applied to the liquid crystal layer by a signal electrode and a counter electrode which are provided on opposed inner surfaces of the two substrates, thereby making it possible to change its optical characteristics (twist of a polarization axis, birefringence property, transmission/scattering, and the like).
Therefore, transmission/absorption or scattering of light, hue, and the like are different between a part where voltage is applied to the liquid crystal layer and a part with no voltage by combination with polarizers disposed on both sides of the liquid crystal cell or the liquid crystal cell itself, whereby various kinds of displays can be performed.
In such liquid crystal display devices, there are a transmission type and a reflection type or a reflection type with illumination. The transmission type liquid crystal display device has a light source part below the first substrate which is opposite to the visible side of the liquid crystal display panel. The reflection type liquid crystal display device has a light source part above the second substrate on the visible side of the liquid crystal display panel, or external light is incident thereon from the visible side.
In the case of the reflection type liquid crystal display device with illumination, a display, during a reflection display, is performed using a difference in strength of light which is made incident on the liquid crystal layer from the second substrate side and reflected from the liquid crystal layer side to go out again to the visible side, and a display similar to the transmission type liquid crystal display device is performed during a transmission display by turning on the light source part below the first substrate.
Further, in a liquid crystal display panel having a liquid crystal layer composed of a twisted nematic (TN) liquid crystal or a super twisted nematic (STN) liquid crystal sandwiched between the pair of transparent substrates, it is necessary to dispose polarizers on both sides thereof, which decreases the transmittance of light, resulting in a dark transmission display.
Accordingly, for example, when the liquid crystal display panel is used as a finder part of a camera, its finder visual field becomes dark in the case such liquid crystal display panel with polarizers is used, because of absorption by the polarizers.
Furthermore, when the environment where the camera is used is dark, the display of the target pattern or the like on the liquid crystal display panel cannot be viewed. If a light source part is therefore disposed on the first substrate side which is opposite to the visible side for illumination, the light from the light source part becomes noise to light from a photographing lens because light from a subject is incident through the photographing lens which is provided on the first substrate side, presenting a problem that the subject becomes difficult to be recognized by the observer.
The present invention is made to solve these problems, and its object is to bring almost the entire display area into a transmission state with high transparency without using a polarizer in the liquid crystal display panel, and to display only a specific pattern in the display area always clearly even when the background is bright or dark and to prevent the background from being hard to view.